1. Field of the Invention
The present invention relates to storage devices in portable systems using rotating storage medium, and more specifically to a method and apparatus for retrieving streams of data from rotating storage mediums while balancing various requirements (e.g., energy consumption, data throughput performance).
2. Related Art
Streams of data (“data streams”) are often stored on rotating storage mediums. For example, a laser compact disc (CD) may store a sequence of digital data elements representing a song. A portable system such as a MP3 player may retrieve the data from a CD, and generate audible signals representing the corresponding song. In general, the medium in such drives rotates while data is retrieved.
Retrieval operations may need to be implemented taking into consideration several requirements. For example, in portable systems, it is usually desirable that the energy consumption be reduced (for retrieval of a data stream) such that a power source (e.g., battery) can be useful for a longer time duration.
One component which consumes substantial energy (watt-hours) while retrieving a data stream, is a rotating structure (in a storage drive). The rotating structure rotates the rotating medium while data is being retrieved. Rotating structures often consume substantial amount of electrical power (watts) as rotation generally involves mechanical tasks requiring use of force. Accordingly, it is generally desirable to minimize energy consumption while retrieving data streams.
In addition, it is often desirable that storage drives support a desired level of data throughput performance (i.e., amount of data retrieved in a unit time, hereafter “performance level”) such that the data is readily available for further use (e.g., to generate audible signals in the case of MP3 system) when needed. A storage drive may support different speeds which can lead to different performance levels with associated different levels of energy consumption.
Thus, using some speeds may lead to consumption of more energy than with using other speeds. However, using some of the speeds may lead to a situation in which sufficient data is not immediately available for use when needed due to, for example, low performance level. Thus performance level and energy consumption requirements may need to be balanced while retrieving data streams from rotating mediums.
While the above scenario is described with respect to a few requirements, there may be several other requirements which need to be balanced while retrieving data. Accordingly, what is needed is a method and apparatus to retrieve data from rotating storage medium while balancing various requirements.